A crown gauge is key equipment for production and control of plates and strips, and plays an important role in improving the yield and quality of plates and strips. As the rolling temperature of hot rolled steel plate/strips is high (over 800° C.), and there are dust, water vapor and the like in the environment, non-contact ray-type measuring methods have great advantages. The performance of the detector of a ray-based crown gauge is one of the key factors determining the measurement accuracy and the detection speed of the crown gauge. Some of the existing crown gauges adopt a single row of solid detectors (as described in the product documents of Thermo Scientific), and in spite of the advantages of high response speed, small size and light weight, also have some shortcomings.
Firstly, the afterglow is long; a photodiode is not irradiation-resistant and has a short service life; the requirement on the working environment temperature is high; and thermostatic control of the working environment is required.
Secondly, as different ray sources share a single row of detectors, a rotating shutter is needed so that two ray sources emit X-ray alternately, and thus the mechanical structure is complicated, and vibration interference occurs.
Thirdly, as rays of two ray sources are measured successively by the same row of detectors, the distance between detected positions of the two ray sources on a steel plate/strip is related to the operating speed of the steel plate/strip, and as thickness reconstruction of the steel plate/strip is obtained by using measured data of the two ray sources, the measurement accuracy is reduced when the operating speed of the steel plate/strip is high.
In addition, a gas ionization chamber detector is adopted in some cases (as described in product documents of IMS Messysteme GmbH), but the ionization chamber used in these cases is large in size, an thus the resolution cannot meet the requirement of steel plants and needs to be increased by oscillating of a C-frame along the width direction of the steel plate/strip. This aspect results in complicated mechanical and control systems; and meanwhile, as the weight of the C-frame is heavy, the swinging frequency should not be too high, generally being 1.5 Hz to 2 Hz, such that when the steel plate/strip moves, data for calculating the thickness on the same cross section are obtained from two different cross sections (with a distance of several to tens of meters), thereby reducing the dynamic performance of the gauge. In the aspect of ray sources, as the field angle of the adopted ray sources is small, and cannot cover the width of the steel plate/strip, a projection needs two ray sources in the width direction of the steel plate/strip, and if ray sources for obtaining another projection are added, four ray sources would be needed in total, so the structure is complicated.